In recent years, as the price of energy sources increases due to the depletion of fossil fuels and the interest of environmental pollution is amplified, the demand for environmentally friendly alternative energy sources has become an indispensable factor for future life. As such, various researches on power generation technologies such as nuclear power, solar power, wind power, and tidal power have been continued, and electric power storage devices for more efficient use of such generated energy have also been attracting much attention.
In particular, with the development of technology and demand for mobile devices, the demand for batteries as energy sources is rapidly increasing, and accordingly, a lot of researches on batteries capable of meeting various demands have been conducted.
Typically, in terms of the shape of the battery, there is a high demand for a prismatic secondary battery and a pouch-type secondary battery that can be applied to products such as mobile phones with a small thickness. In terms of materials, there is a high demand for lithium secondary batteries such as lithium ion batteries and lithium ion polymer batteries having advantages such as high energy density, discharge voltage, and output stability.
In general, such a secondary battery is formed in a structure such that an electrode assembly including a positive electrode, a negative electrode, and a separator disposed therebetween is built in a battery case, and positive and negative electrode tabs are welded to two electrode leads and are sealed to be exposed to the outside of the battery case. The electrode lead is electrically connected to the external device through contact with the external device, and the secondary battery supplies power to the external device through the electrode lead or receives power from the external device.
Meanwhile, the secondary battery is manufactured by accommodating an electrode assembly in a battery case and injecting electrolyte, followed by a battery activation step. At this time, the battery activation step includes the process of charging and discharging the secondary battery in the conditions necessary for activation after mounting the secondary battery in a device for charging and discharging a secondary battery. Such a secondary battery charging and discharging device is mainly used to charge or discharge the secondary battery in the battery activation step, as well as used for performance evaluation purposes of the secondary battery.
However, in order to properly charge or discharge the secondary battery using the secondary battery charging and discharging device, the secondary battery should be properly mounted on the secondary battery charging and discharging device. That is, the electrode lead of the secondary battery is disposed to contact the conductive portion of the secondary battery charging and discharging device so that both are electrically connected, and the electrical connection state should be maintained while charging and discharging is in progress.
The secondary battery charging and discharging device for this purpose is generally provided with a fixing jig for fixing the electrode lead. During charging and discharging of the secondary battery, when the fixing jigs 10 and 20 of the conventional electrode leads are applied as shown in FIG. 1, the fastening method of the battery cell becomes not the same, and thus the resistance is changed depending on the fastening method.
Specifically, as shown in FIGS. 2 to 4, when the electrode lead film 62 is in contact with the jigs 10 and 20, a large contact resistance is generated, and a difference in contact resistance occurs depending on the length of the electrode lead 61 due to the electrode lead 61 being fastened in a deviated manner or the electrode lead 61 being excessively inserted or not sufficiently inserted into the jigs 10 and 20. As a result, in spite of fastening the same battery cell to the jig, a problem arises in that the experimental results vary depending on how the battery cell is fastened.
Thus, in order to accurately perform an experiment, it is necessary to develop a charge/discharge device capable of fastening the battery cells equally in every experiment.